Electrosurgical instruments of the type mentioned at the beginning are used for cutting or coagulating tissue using high-frequency alternating current. Argon plasma coagulation (APC) is a special application form of electrosurgery in which high-frequency current is transferred in a contact-free manner through ionized argon gas.
The energy input is effected in the known instrument mentioned at the beginning by changing the exposed length of the electrode. To accomplish this, an axial movable outer shaft is provided that surrounds the electrode and insulates it and that can be displaced along the electrode to expose it as needed.
A central requirement on such instruments is that they allow one-hand operation. When this is done, the position of the instrument in the operating field should, to the extent possible, not change. This means that the grip should be maintained to the extent possible during operation of the instrument, even when the outer shaft is displaced.
In the instrument of the type mentioned, this is achieved by a rotating wheel that is centrally arranged in the handle of the instrument and that can be actuated with the index finger. The rotating wheel drives the outer shaft, which can, as a result, be axially displaced along the electrode.
The outer shaft of the known instrument is rigid and extends straight in the distal direction. In the case of certain applications, it is desirable for the shaft to be bent at an angle. It is true that there are APC applicators with flexible tips for this purpose. However, the tips must be manually bent at the desired angle before use. It is impossible to change the angle during use.